1. Field of the Invention
This invention is related to an optical switching apparatus used in an optical network for voice and data communications. More particularly, embodiments of the present invention provide for an optical switching device with adiabatic coupling to an optical fiber and method for fabricating an optical switching device with an adiabatic coupling structure.
2. Description of the Related Art
Strong growth of optical networks for voice and data communication results in huge demand for high data rate information transfer capabilities. To enable such transfer capabilities, dense wavelength division multiplexing (DWDM) technology has been developed which allows transfer of multiple wavelength over the same fiber leading to data transfer rates up to 40-100 Gb/s. High speed switching and routing devices comprise the core elements of the optical networks and allow dynamic control of the data traveling over the optical network. Furthermore, high data transmission rates impose strong requirements on the functionality of the switching devices.
Optical cross-connect space division switches based on optic-electro (OE) deflection of the light beam have great potential for future implementation in high speed optical networks. One of the basic concerns is the switching time and a capability of handling a great number of input and output channels, e.g., up to 4000×4000 by the year 2003, as well as reliability and cost factors. Existing optical switching devices which employ signal conversion from optical into electrical and back into optical do not satisfy those requirements. Having very low switching times switching matrixes can be designed to connect very large number of input and output (I/O) ports. Such switches may be built from an assembly of simple digital optical switches where each can redirect one input signal into two possible output ports. However, optical cross-connect switching elements are more useful for large-scale implementations. These devices require large-scale monolithic switch arrays to perform switching functions. Although, the main principle of the optical cross connect switching based on the light beam deflection is well known, a robust, reliable, low cost and extendable integration process for such type of switching device is not available.
Currently, the main optical switching products on the market (e.g. Lucent's Lambda-router) are based on MEONIS technology, which employs rotating micro-mirrors to deflect light. However, these optical switching devices are not very reliable due to many moving parts, and also the switching time is limited by the mechanics of the mirrors. It is desirable to improve the reliability of the many moving parts of the optical switching devices and to overcome the limitation of the switching time in these devices due to the mechanics of the micro-mirrors.
There are several other optical switching technologies which are still not well represented in the market due to various technological and economic difficulties. Such optical switching technologies include by way of example only: the bubble switch from Agilent Technologies Inc., switches based on liquid crystals, and thermo-optic and electro-optic (EO) effects, etc. Most of these devices are still in the R&D stage. Some of those technologies including EO switches may be applicable for high speed, low cost, high reliability, and high I/O port count products.
Especially, thin film electro-optic (EO) devices provide a number of advantages compared to their bulk material counterparts. There are a number of requirements which have to be satisfied for a fabrication of a high quality EO device for optical signal transmission. First, a waveguide with a core layer and two cladding layers should be formed to allow a low-loss propagation of a light beam. Second, an active material should have a high EO coefficient for the correct functionality. Third, for a number of the device types the thickness of EO material should be in a very narrow range (5-10 μm) in order to reduce the applied voltage needed for the EO change of the material refractive index (RI) and at the same time to allow low-loss coupling between a light beam coming out of an optical fiber and an optical switching device.
Therefore, what is needed and what has been invented is an improved optical switching device and method for fabricating the improved optical switching device. What is further needed and what has been invented is a tapered structure in a coupling structure of an optical fiber and an optical switching device and a fabrication process of the tapered structure in a coupling structure of an optical fiber and an optical switching device.